1. Field of the Invention
This invention relates to orthodontic headgear, and more particularly to a connector for exerting extraoral force from such headgear to the jaw of the wearer, which connector can be adjusted to provide extraoral force of different degrees and which connector is disconnectible if a force exceeding a predetermined force is exerted on it.
2. Prior Art
Armstrong U.S. Pat. No. 3,526,035, issued Sept. 1, 1970, discloses an orthodontic headgear including a spring which produces an extraoral force the degree of which force is indicated by calibrations.
Later Armstrong U.S. Pat. Nos. 4,115,921, issued Sept. 26, 1978, and 4,155,161, issued May 22, 1979, show extraoral headgears for producing an extraoral force including connectors which are disconnectible when a force exceeding a predetermined force is exerted on them.
Klein U.S. Pat. No. 4,226,589, issued Oct. 7, 1980, discloses a disconnectible orthodontic headgear connector including a return bent spring clip forming a disconnectible connector. The force produced by such connector, however, results from an elastic band or a spring of cross-leg type which is unsatisfactory. Moreover, the travel of the disconnectible parts prior to disconnection is excessive, the minimum force which will effect disconnection is difficult to establish precisely, and the value of such force cannot be altered.
The still later Armstrong U.S. Pat. No. 4,238,188 issued Dec. 9, 1980, discloses a disconnectible connector employing a compression spring for producing an orthodontic force with means for adjusting such force and with a disconnectible connection, but such device is of considerable length.
Armstrong U.S. Pat. No. 4,368,039, issued Jan. 11, 1983 and U.S. Pat. No. 4,416,625, issued Nov. 22, 1983, which resulted from a continuation-in-part application of the application maturing into U.S. Pat. No. 4,368,039, disclose a different type of mechanism for adjusting the extraoral force produced by an orthodontic headgear connector.
Also a disconnectible connector incorporating a helical compression spring is shown in the publication High-Pull Traction Release System of Unitek Corporation bearing the copyright notice date of 1979.